Drive chains are commonly used on vehicles having a track drive and typically include a chain bushing, a pin extending through the chain bushing and having an end projecting beyond the bushing and two chain links which are linked together by the pin and bushing on each side thereof. The chain links disposed on opposite sides of the chain bushing are overlapped in order to provide an inner chain link which is pressed onto the bushing and an outer chain link which is pressed onto the axially extending end of the pin.
Drive chains of this type are widely used in track vehicles such as construction vehicles, earth moving vehicles, and other special purpose vehicles. To reduce the friction, and thus reduce adhesive wear and minimize the overall wear, which can lead to chain lengthening and which can decrease the life of the chain or link assemblies, the hinge joints are lubricated with grease or oil containing additives which limit corrosion and increase the lubricant life. Track vehicles are typically operated and even have maintenance performed in very dirty environments in which there is a significant chance of contaminating dirt getting within the sealed environment. In particular, chain preventative maintenance typically consists of dismantling each and every link in the chain and rotating the bushings 180 degrees to distribute wear from the drive sprockets, which only wear against one half of the outer surface of the bushings at a time. With presently used seal designs, this assembly and re-assembly process inevitably contaminates the dynamic sealing surfaces of both the mechanical face seal head and the ends of the bushings that serve as the sealing counterface or seal seat for the seal. After field preventative maintenance is completed, the contamination trapped between the mechanical face seal head and the bushing seal seat surface can separate these sealing surfaces and/or cause their abrasive destruction. If the seals are destroyed, the seal's ability to retain lubricant internal of the seal and exclude external abrasives and liquids from entering the seal system and contaminating the lubricant is also destroyed. The loss or contamination of the oil that lubricates between the drive bushing and link pins, in turn causes wear and failure of these components, and the drive train.
Accordingly, it is an object of the present invention to provide a seal assembly that is capable of increasing the life of the sealing system and also facilitates field preventative maintenance in which the bushings are rotated. The system of the present invention provide a spacer sleeve that is disposed on the pin and provides a sealed relationship between the inner and outer links of a drive chain. A seal seat member is disposed on a first end of the spacer sleeve and a grommet member is disposed on the seal seat for engagement with a bore in the end of the bushing. A seal washer is disposed on the spacer sleeve adjacent to the seal seat member and a second seal member in the form of an elastomeric boot is seated on the seal washer. A spring seat is disposed on a second end of the spacer sleeve and supports a portion of the second seal member. A spring is disposed between the spring seat and the seal washer for biasing the spring seat and the attached portion of the second seal member against the mating bore portion of the outer link. The removal of the seal head portion, which is comprised of the elastomeric boot, spring seat, spring and seal washer from the outer link bore causes the as installed clearance passageways between the seal head and seat portions and the spacer to forcefully close and prevent abrasive particles from getting inside the seal and reaching the interior interface junction of the dynamic sealing surfaces. A radial lip seal portion of the seal seat extends and seals around the seal washer outer diameter to prevent abrasive particles from reaching the exterior interface junction of the dynamic sealing surfaces.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.